Co-absorption and Reduction Mechanism of SO 2 and NO 2 from Flue Gas Using a Na 2 SO 3 Solution with an Oxidation Inhibitor

Abstract

Herein, a novel Na₂SO₃ process enhanced with an oxidation inhibitor was proposed for the synergic removal of SO₂ and NO₂ from nonferrous smelting flue gas. The co-absorption and reduction characteristics and mechanism of SO₂ and NO₂ were investigated. Results showed that when 80.59, 161.17, and 241.76 mM Na₂S₂O₃ was added into 2% of Na₂SO₃ solution, NO₂ absorption capacity increased to 264%, 300%, and 330%, and that of SO₂ increased to 162%, 198%, and 232%, respectively. The inhibition action of Na₂S₂O₃ was achieved by reacting $S_2{O}_3^{2-}$ with $\bullet {SO}_3^{-}$ to form an inert substance polythionate that prevents $\bullet {SO}_3^{-}$ from reacting with dissolved oxygen. The co-absorption and reduction characteristics of SO₂ and NO₂ revealed that ∼42.5% of NO₂(N) was reduced to N₂, 21.5% of NO₂(N) combined with ${SO}_3^{2-}$ to form ${ONSO}_3^{-}$ compounds, 5% of NO₂(N) formed ${NO}_3^{-}$ in solution, and 22.6% of NO₂(N) was reduced to NO into flue gas. Therefore, the enhanced Na₂SO₃ process shows potential for synergistic desulfurization and NO₂ removal from the nonferrous metal smelting industry.